The present invention relates to an improvement in skis used on snowmobiles or other vehicles to facilitate forward movement and steering, more particularly to an adjustable flex dampened ski.
Typical snowmobiles are powered by a front mounted engine attached to a rear endless track system. The track on conventional snowmobiles is suspended using springs and gas powered shocks to absorb the bumps and aid in control and handling of the snowmobile. These snowmobiles are typically supplied with two skis attached to a rider operated steering system. The skis are placed in front of the track system and are, thus, the first part of the vehicle to meet obstacles such as rocks, logs and bumps. Different manufacturers have developed and utilized several different means of adding travel to each individual ski system. These systems range from a wishbone type suspension to an upright spring and dampener type system.
The classic, or conventional, snowmobile ski is constructed of metal and attaches to the steering system mechanism at a point near the middle of the ski. These skis are typically curved upward at the forward portion which allows the ski to ride over obstacles. The curved portion also aids the ski in traveling through snow conditions ranging from deep powder snow to slush and ice. These metal skis also have bridges or bars running along their length for stability and strength.
A stiff loop, made of metal rods, is typically attached to the front portion of the ski near the top of the front curved section. Some skis have used a piece of angle iron or bracketing to increase the strength of the loop. This rod or loop is then attached in a circular fashion back towards the center portion of the ski. The loop has several purposes, the first of which is to strengthen the ski. The loops also act as a continuation of the curved portion of the ski and, thus, enhances the skis ability to handle bumps, moguls or obstacles. These loops have also evolved into handles to aid in moving the snowmobile or picking up the front for a variety of reasons.
The metal ski has been standard for many years, but recently the industry has begun adopting skis made of metal bridges, reinforcements and plastic portions. This plastic may be of a type such as an Ultra High Molecular Weight Polyethylene (UHMW) or (UHMW-PE) plastic. This type of ski has been developed to overcome some of the disadvantages of the metal ski and to provide a lower coefficient of friction. One of these disadvantages has been that metal skis are unyielding and thus, subject to denting and bending as the ski is used in normal operation. This bending and denting eventually leads to a drop in performance of the ski and often necessitates the replacement of the ski. The use of flexible and resilient plastics has resulted in skis that are durable and able to withstand impacts that would have damaged conventional metal skis. These skis, however, are made with metal bridges, saddles or supports that result in a ski that, although resilient at it edges, is overall rigid. The problem with a ski that is overall rigid, is that when the tip of the ski encounters a bump or obstacle, the ski's lack of ability to flex will cause the surface of the ski that is in contact with the snow to rise and, thus, lose contact with the snow. The result of this is that the ski's loss of contact with the ground or snow will substantially affect the riders ability to control the vehicle, as it will tend to dart from side to side as the steering and control of the snowmobile is placed entirely upon that portion of the ski which remains in contact with the ground.
U.S. Pat. No. 5,040,818 issued to Metheny on Aug. 20, 1991, and U.S. Pat. No. 5,145,201 issued to Metheny on Sep. 8, 1992, a continuation in part issuing from the 818' patent, generally discloses one of the current plastic and metal skis. This ski has a formed plastic base with a metal bridge and saddle top. The front tip of the ski in one embodiment is equipped with a solid loop and upper bridge which holds the front of the ski in a curved and rigid form. In this embodiment the ski is substantially rigid and thus, suffers from the same handling characteristics as the metal ski in bumps. A second embodiment of this ski uses a rigid rod of adjustable length which may be used to vary the upward curvature of the ski as the rod is lengthened or shortened. This embodiment has some flex, however, the flex tends to be behind the rods connection point and in front of the metal saddle, at one point on top of the ski. This tendency to flex at one point, as the rod is solid, results in a ski that flexes too much to the point that it is damaged or broken by severe impacts such as logs or rocks, and can create a dangerous and expensive situation for the rider.
Another ski of the plastic variety is shown in U.S. Pat. No. 5,360,220 issued to Simmons on Nov. 1, 1994. This patent discloses a ski having a plastic curved base. The base has a flexible loop attached to the underside of the front and up and over the tip of the ski to a point on the upper base of the ski near the middle. The loop is attached near the middle of the ski in a slidable fashion such that the ski may flex. This configuration works to make the ski somewhat flexible, however, as the ski is pre-curved the flex is not adjustable. The loop acts to evenly distribute the bending and flexing of the ski over a large area. Although this works to alleviate the problems of flex in one point and thus prevent breakage, this design is not adjustable to a given riders size or preference. The ski operates at a preset flex within certain limits. Thus, a rider may still experience problems in bumps with darting, as the ski may be too soft for a large rider or too stiff for a small rider and, thus, flex to a point, or not flex, such that the rear portion of the ski leaves the ground and reduces a riders control of the sled.
From this discussion it can be seen that it is desirable to supply a ski that works to absorb bumps during riding. It is also desirable to make this ski adjustable to riders of a given weight and different riding styles. Further it is necessary that this ski be designed to flex evenly throughout its length so that the ski will not buckle under extreme bumps such as ditches, logs and rocks.